Process and apparatus for the conversion of molten metals or metal alloys



Dee. 29, 1942.

o. LANDGRAF 2,306,449 PROCESS AND APPARATUS FOR THE CONVERSION OF MOLTENMETALS OR METAL ALLOYS Filed OGL 10, 1940 Patented Dec. 29, 1942 PROCESSAND APPARATUS FOR, THE CON- VERSIYCgN OE MOLTEN- METALS OR METAL OttoLandgraf, Frankfort-on the-Main, Germany; vested in the Alien PropertyCustodian Application October 10, 1940. Serial No. 360,650 In GermanyOctober 14, 1939 9Claims.

It is knfin to convert metals or metal alloys into a finely divided formby impinging themolten substances on the rotating disc whilst coolingwater or the like is simultaneously sprayed on the disc. Depending onthe speed of rotation of the disc and the kind of cooling the impingedsubstance is converted into more or less finely divided particles.Thereby a mixture of differently sized grains, 1. e.. fine and coarsepowder, is obtained. This difference in the size of grains requires anew operation step. as the material must be sieved or sifted in order toobtain a metal powder with nearly uniformly sized grains. It has alreadybeen proposed to arrange the rotatingelements in a stepped ordiscontinued manner but the powder obtained was yet difierently sizedand involved a subsequent sieving or sifting if a powder with a specialfineness was required.

Object of; my invention is asubstantial increase in the share of aspecial narrow area of grain sizes, without any subsequent'sieving orsifting operation so that a powder with particles of a definite finenessis obtained. A further object of my invention is the preliminarydetermination of the narrow area of the desired grain size.

Now I have found that a rather large quantity of nearly equally sizedsubdivided grain particles may be obtained if at least tworotating-elements are employed to comminute the molten good. It hasproved expedient to arrange the rotating elements in such manner thatthe particles propelled off by one rotating 'disc are impinged on theother disc and finely divided until solidification, Another object of myinvention lies in the fact that the rotating elements are independentfrom each other, moving with different speed against each' other.

The scope of my invention may be explained as follows: The molten goodimpinges on the first rotating element and is comminuted. The smallestparticlessolidify at once and are propelled ofi without any furtherdivision on the next rotating element. The larger particles whichprobably due to the heat insulating effect of the enclosinz. watervapor, impinge in a liquid state on the next rotating element aresubject. to a further subdivision and will yield to a grain size nearlyequal to the smallest particles of the first rotating element. Thecomminution may be continued till R5 the all droplets are solidified andno new subdivision may take place.

In most cases two superposed rotating elements will be'sufiicient. Thecountercurrent speed of 5 the rotating elements is so great that theimpact of the centrifuged particles on the second rotating disc is soheavy that no more rotating elements are necessary. The finely grainedparticles coming fromthe first rotating element are nearly allsolidified, thus forming already the final product. In contrast to theknown rotating elements withribs or the! like it is an essential featureof the new invention that the particles propelled oil from the firstrotating element are 5 impinging .with an increased vehemence on thesecond rotating disc. The hitherto known rotating elements are providedwith different steps.

ribs or the like on the same disc and have therefore no relativevelocity against each other. The

limit of the smallest diameter of the particles is obtained through therotating speed of the first all 35 erated deduction of heat may takeplace. This avoids an adherence of the molten good through burning in onthe beating blades. I have observed that the rotating elements accordingto I my invention remain perfectly clean after use. 40 Even after aseveral months utilization there was no remarkable wear, although onepart of the material leaving the first rotating element, impinges in anearly or wholly solidified state on the next rotating element.

Ii according to my invention more rotating elements moving withcountercurrent or varied speed are used, the yield of an uniform productis i'ar greater than thus obtained with the hitherto known singlerapidlyi rotating disc. Thecomminution of aluminium. for instance,attains a three times increased yield of finely divided particles(10,000 mesh/qcm.)

To-increase the vehemence of impact of the particles coming from thefirst rotating element,

rotating element may be moved in counterhowever, the superposed rotatingelements are concentrically arranged, i. e., coincide, thecountercurrent is obtained by the impellers and blade wheels, in casethe rotating-elements move in countercurrent Expediently; therotatingelements superpose in their blades or wings. The size of therotating elements is not prescribed but I prefer to use rotatingelements of thesame size.- If, however, rotating elements are used withdifferent diameters, whereby in adisplaced arrangement the secondrotating element is greater than the first, the openings of therotating; elements must cover each other. speed of the elements may beequalorriiifierent, according to the respective requirements. 'The gradeof fineness will be obtained by the .-rotating speed of the firstrotating element. If. the disc rotates slowly the comminutlonwill yieldto coarse grains which, however, will be of substantially the same size.

In order to obtain a perfectly uniform .product it is necessary that thematerial is applied in a molten state and-that the casting jetisprotected against cooling before it impinges on the first rotatingelement. Simultaneously with'the corn.- minution strong cooling. is.obtained by application of a-cooling medium such as water. ortthe like.Thereby I may proceed; for instance, in such manner thatsimultaneouslywith the molten material a cooling liquid is sprayed onthe The rotating ments wherebythe latter may have diiferent or equaldiameters.

The impulse of the rotating elements may be utilized anyhow whereby therotating elements may run with the same or different speed. Thus, forinstance, the subsequent rotating elements may have a higher velocitythan the first, thereby increasing the impact force.

The casting jet is directed against the part of the first rotatingelement which is equipped with beating organs. The material iscomminuted by the impact force and particles of various sizes areobtained. The smallest particles solidify at once. Owing totheir largevolume the greater particles remain in a molten state. Impinging on thenext rotating element the solidified small- .erpartlcles are onlypropelled of! but not subiectecl to a further comminution. The greater,particles are again divided whereby the finer rotating element whereby.the'- rotating element is at the same time also cooled. Through; theexplosion like evaporation of the cooling. liquid the comminution of themolten metal. is promoted and a favorable vapor atmosphere isproduced.If desired, the walls of the comminution vessel may be cooled also.Instead of orbesides a cooling liquid a. gas-may also. be employed. If agas is used an inert. atmosphere will be-produced which has provedadvantageous with melts of base metals. Nitrogen, carbon dioxide,.hydro-*gen, generator gas, illuminating gas and the like may also be employedas cooling media.

A few embodiments of the invention are illustrated .in the annexeddiagrammatical drawing. Figures 1 and 2 show forms of the rotatingelements. Figures 3 and 4 show a side view and a plan view of oneembodiment of the rotating element.

' The rotating elements I are placed in as near a distance as possibleand are equipped with radially directed propellers, blades 2 or thelike. The propellers or blades of the rotating element are moving incountercurrent. The direction of rotation depends upon the arrangementof the rotating elements as a whole. Displaced, the countercurrent isobtained through rotation in the same direction, as in this case thepropellers or blades move in contrary direction against each other. If,however, the axes of the rotating elements coincide, the movement of therotating to obtain a countercurrent effect. axes displacement is to bechosen'in such manner that the parts of the rotating elements which areprovided with propellers and blades are overlapping (see Fig. l). Thedistance between the axes depends upon the size of the rotatingelegrains solidify immediately. If necessary, more rotating elements maybe.provided= to: further comminute the liquid coarser particles on thesecond rotating element. In'this manner. a-large amountof particles:with thesame. or nearly'the same grain size will be obtained'Inpractice, two rotating elements will be suiiloient.

The beating'clements 2 maybe-constructed as shown in Figs. 3 and 4.

The blades 3 of the heating elements show such a direction that themolten'material or particles are centrifuged to thenext-rotating'element. The planes may ithereby-.-bei--inciinedobliquely. It has proved.advantageous-tolmake the beating armsrelatively strongand broad in order to avoid aburninginofthe=molten.-material. This makes an increaseddeduction of theheat possible so that'the materialhas-no time toadhere. The beatingelementsmay'also betapered against the direction pf-rotationr'lhisprocedure prevents that the molten material is spattered sideways.without impinging- .on the beating areas.

The rotating elements are-(advantageously providedwith a largerquantityof heating elements closely arranged at-theperipheryofxthezrotating elements. The propellers: and blades-may be plane orcurved. It is essentialronly thatallthe material impinges directlyonthe: blades and is propelled off in the'direcizlonof thenext rotatingelement.

What I claim is:

l. A process for theconvers'ion. of molten metal into fine particles ofsubstantially-.uniformsize. which comprises impinginga rstreamptmoltenmetal against a rapidlyrotatingbeating. surface and simultaneouslyimpellingzthe resulting subdivided metal dlrectly againsta furtherrapidly rotating beating and impellingsurface, while supplying a streamof cooling 'liquidto r-the'first elements must be contrary to each otherin order The size of rotating surface simultaneouslmwith said stream.

of molten metal.

2. A process for the conversion of molten-metal into fine particles ofsubstantially uniform size, which comprises impinging a; stream ofmolten metal downwardly against a rapidly-rotating beating surface andsimultaneously impelling the resulting subdivided metal .d'ownwardlydirectly against a further rapidly 'rotating..beating. and impellingsurface. while supply ng. a stream of cooling liquid to thefirstrotating surface simultaneously with said stream of molten metal.

3. A process for the conversion of molten metal into fine particles ofsubstantially uniformsize. which comprises impinging a stream-of moltenmetal downwardly against a rapidly rotating 'molten metal downwardlyagainst a rapidly rotating heating surface and simultaneously im-'pelling the resulting subdivided metal downwardly directly against afurther rapidly rotating beating and impelling surface, while supplyinga stream of cooling liquid to the first rotating surface simultaneouslywith said stream of molten metal, and causing the subdivided metalparticles to be impelled upon rapidly rotating beating and impellingsurfaces until they have solidified.

5. An apparatus for the conversion of molten metal into fine particlesof substantially uniform size, which comprises .a rotating element forbeating and impelling downwardly material supplied from above, means forsupplying a stream of molten metal to said rotating element, means forsupplying a stream of cooling liquid to said rotating elementsimultaneously wi h said stream of molten metal, and a second rotatingelement for beating material impelleddownwardly thereto directly in thepath of the metal impelled downwardly by the first rotating element.

6. An apparatus for the conversion of molten metal into fine particlesof substantially uniform size, which comprises a rotary element, meansfor supplying a stream of molten metal to such rotary element, means forsupplying a stream of cooling liquid to said rotary elementsimultaneously with said'stream of molten metal, beating means on saidrotary element for impelling the metal supplied to the elementdownwardly.

and a second rotary element provided with beating means directly inthepath of the metal impelled downwardly by the beating means upon thefirst rotary element.

7. An apparatus for the conversion of molten metal into fine particlesof substantially uniform size, which comprises a series of superposedrotary elements, means for supplying a stream of molten metal downwardlyto the uppermost rotary element of such series, means for supplying astream of cooling liquid to the uppermost rotary element simultaneouslywith said stream of molten metal, said rotary elements being providedwith beating blades which impel the metal being treated downwardly anddirectly against the beating blades of the rotary element next in theseries.

8. An apparatus for the conversion of molten metal into fine particlesof substantially uniform size. which comprises a rotary element havingimpelling blades, means for rotating the rotary element in apredetermined direction, means for supplying a stream of cooling liquiddownwardly to said rotary element, and means for supplying coolingliquid to the rotary element simultaneouslywith' said stream of moltenmetal, said impelling blades impelling downwardly the molten metalsupplied to the rotary element upon rotation in said predetermineddirection, and a seccnd rotary element having impelling blades directlyin the path of the metal impelled downwardly by the impelling blades ofsaid first rotary element.

9. An apparatus for the conversion of molten metal into fine particlesof substantially uniform size, which comprises a rotating element forbeating and impelling downwardly material supplied from above, means forsupplying a stream of molten metal to said rotating element, means forsupplying a stream of cooling liquid to said rotating elementsimultaneously with said stream of molten metal, and a second rotatingelement.

OTTQ LANDGRAFL

